问题 选择题

某同学用托盘天平称量时(1g以下用游码),两托盘上各放一张质量相同的纸,左盘放11g砝码,游码在0.6g处,右盘加入食盐达到平衡,则实际称取的食盐质量是(  )

A.12.2g

B.11.6g

C.11g

D.10.4g

答案

由用托盘天平称量氯化钠药品,可知砝码质量为11g,游码质量为0.6g,再根据左盘的质量=右盘的质量+游码的质量

即11g=药品质量+0.6g,所以氯化钠药品实际质量=11g-0.6g=10.4g.

故选D.

阅读理解

阅读短文,根据其内容回答问题。

     Five million people visit Grand Canyon in the US every year. For the purpose of helping protect Grand

Canyon for your fellow visitors and future generations, please follow the guidelines below.

     Camping To protect the park, camping is allowed only within permitted camp-grounds. Permits are

required for ovemight camping at the North Rim. Advance book- ing can be received by mail. Please write:

Information Center, P.O. Box 129, Crand Canyon, AZ 86023.

     Fires Because of the extreme fire danger, campfires are not allowed except at Mather and Desert View

campgrounds. Collection of firewood is not allowed either.

     Hiking Please stay on permitted paths. Otherwise you may destroy desert plants. Pack out what you

pack in, so you leave no signs of your visit. It is important to keep in mind that you are in a national park

where wildlife exists.

     Weather The weather at Grand Canyon can change very quickly. With so much rock, lightning (闪电)

causes a particular danger during sudden summer storms. These storms also frequently bring floods inside

valleys, a danger to hikers. Watch the skies and check daily weather reports.

     Wildlife Do not feed park wildlife. There have been a few cases at Grand Canyon National Park where

deer were purposely shot because there are plastic bags that left them sick and weak. Hungry deer can be

danger and have kicked and bitten visitors at Grand Canyon. Some other animals will also beg and bite. For

your own safety and the well-being of the animals, please do not feed wildlife, no matter how gentle they

may appear.

1. Do five million people visit Grand Canyon in the US every year?

    ____________________________________________________________________

2. Why aren't campfires allowed except at Mather and Desert View campgrounds? 

    ____________________________________________________________________

3. How is the weather at Grand Canyon? 

    ____________________________________________________________________

4. How many guidelines are there in this passage? 

    ____________________________________________________________________

5. What is the main purpose of the passage? 

    ____________________________________________________________________

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